Fighter Martial Archetype: Shield Wall
Fighters of the shield wall are consummate defenders and front-line soldiers, training relentlessly with their shields to form near-impenetrable human barriers that only grow stronger together.
But what any instructor worth their salt will tell you; a shield is akin to a second weapon, used just as much for offence as for defence.
Hold the Line
When you choose this archetype at 3rd level, you learn how to plant yourself on the battlefield, claiming your spot and letting none overtake you. You enter this battle stance as a bonus action, and it lasts until you end it as another bonus action, are knocked prone, or otherwise incapacitated.
While Holding the Line, your base walking speed is reduced to 5ft and you have disadvantage on weapon attack rolls. You do however gain advantage on saving throws against effects that would knock you prone or otherwise move you, as well as against damaging spell effects like the fireball spell.
Additionally, while you are within 5ft of an ally that is wielding a shield, you form a shield wall to gain +1 to your AC (this bonus stacks).
Shield Bash
At 3rd level, you learn to wield your shield as a weapon as well as a defensive tool. A shield for you counts as a melee weapon with 5 feet of reach, dealing 1d6 bludgeoning damage on a hit, and you are proficient with this weapon. When you make an attack with a one-handed weapon you are holding as part of the Attack action, you can make one melee weapon attack with your shield as a bonus action.
Shield Bash attacks do not suffer from the disadvantage imposed from Hold the Line.
Repel Invaders
Beginning at 7th level, when you hit a creature with a Shield Bash attack, you may choose to force them to make a Strength saving throw (DC = 8 + your proficiency bonus + your Strength modifier). If they fail, they are pushed away 5ft from you. Making further attacks against a creature that has been pushed in this way does not suffer from Hold the Line’s attack disadvantage for that turn.
You may push a creature in this way once per turn.
Living Barricade
From 10th level, you grant half cover to allies behind your shield wall when Holding the Line.
Together as One
At 15th level, friendly creatures within 5 feet of you who are holding a shield can choose to gain the benefits (and penalties) of your Hold the Line feature while you are in that stance. They may then extend the shield wall to eligible friendly creatures next to them in turn.
Allies attacking from behind your shield wall gain advantage on attack rolls against creatures within 5ft of the wall.
Wall of Steel
At 18th level, you let nothing get past your shield wall. Allies benefitting from your Living Barricade feature now gain three-quarters cover.